class Solution {
public:
    int minimumDeleteSum(string s1, string s2) {
        int sum = 0;
        for(auto& e : s1)
            sum += e;
        for(auto& e : s2)
            sum += e;
        int m = s1.size(), n = s2.size();
        s1 = " " + s1, s2 = " " + s2;
        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
        // dp[i][j]表示s1的[0, i]区间以及s2的[0, j]区间内的所有的子序列中，
        // 公共子序列的 ASCII 最大和。
        for(int i = 1; i <= m; ++i)
        {
            for(int j = 1; j <= n; ++j)
            {
                if(s1[i] == s2[j])
                    dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + s1[i]);
                else // ((s1[i] != s2[j]))
                    dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
            }
        }
        return sum - 2 * dp[m][n];
    }
};